Although technological change is a hallmark of health care worldwide, relatively little evidence exists on whether changes in health care differ across the very different health care systems of developed countries. We present new comparative evidence on heart attack care in seventeen countries showing that technological change--changes in medical treatments that affect the quality and cost of care--is universal but has differed greatly around the world. Differences in treatment rates are greatest for costly medical technologies, where strict financing limits and other policies to restrict adoption of intensive technologies have been associated with divergences in medical practices over time. Countries appear to differ systematically in the time at which intensive cardiac procedures began to be widely used and in the rate of growth of the procedures. The differences appear to be related to economic and regulatory incentives of the health care systems and may have important economic and health consequences.